Certain medical conditions require patients to self-administer medicament(s) over a long period of time, perhaps years. Where possible such medicaments will be formulated for oral delivery which helps with patient compliance. Due to the nature of the medicament (e.g. insulin) oral delivery is not always possible and other administration routes are necessary. Self administration by injection is not ideal, inter alia for reasons of accurate dosing and patient compliance (needle-phobia being relatively common), but oftentimes necessary.
Over recent years there has been significant development in the area of injectors. In particular electro-mechanical injectors are now available. Such devices are generally battery powered and designed for multiple uses. The devices generally comprise a housing having a motor-driven piston which acts on a cartridge containing the medicament to be delivered through a needle attached to the device (although it will be understood that “electro-mechanical device” includes any device that requires power for any reason, irrespective of whether medicament delivery is by electro-mechanical or purely mechanical means). The device may have a graphical display for displaying such information as device status (e.g. ready for injection, cartridge empty, error status, dosing history etc.) a user interface (usually one or more buttons) for entering a required dose, initiating dosing and/or priming and powering up/down the device and a microprocessor for controlling the motor(s) according to a user defined dose, monitoring error conditions, writing dose histories to memory etc.
Certain devices are available for delivering a combination of two medicaments from separate cartridges, each cartridge being driven by a separate motor. For ease of use the display and the user interface may be illuminated. It will therefore be appreciated that there can be a significant power demand from such devices. There is therefore a need to minimise the power drawn by such devices, particularly when not in use between injections, a state in which the device will spend most of its time, to extend the interval between battery charges or replacement. The present invention is conceived with this problem in mind.
The users of devices with which the present invention is concerned may have complicating medical conditions. Lack of manual dexterity, visual impairment and memory loss are not uncommon. Thus, any solution to powering down the device should ideally not require any additional specific tasks for the user.
Devices are known that simply use the presence of a cap to power down the device. For example the Innovo™ device previously sold and marketed by Novo Nordisk uses a tab in the cap to prise apart two contacts in the housing. The tab inserts into a slot in the surface of the housing. This has the disadvantage of potentially allowing the ingress of moisture or dust into the housing or requires a gasket or other means to seal the slot. A significant advantage of the present invention is that the contactless nature of the switch means that no additional openings for potential ingress of water or dust are created. Moreover, there is always the risk that a mechanical switch will fail through repeated use.
WO 2006/032614 describes an injection device with a cap, such that when the cap is placed onto the device, the device switches between an injection mode and a set-up mode. Both modes are controlled by a common electrical circuit. With the cap on the device, the device must either be manually turned off, or a time-out feature must be used to switch off the device. Both of these solutions lead to unnecessary on-time for the device.